Squashed 'bundle/vim-airline/' content from commit fae68db

git-subtree-dir: bundle/vim-airline
git-subtree-split: fae68dbcb74b3d7a3144a9b57253b5051f26e207
Merge commit 'e9bcf45dcf162946d170bc5bd5b31048e078cd3c' as 'bundle/vim-airline'
Set vim-airline to use powerline symbols